Crystal starter rectifier and phase control tube



April 27, 1937. D. D. KNOWLES I 2,078,671

CRYSTAL STARTER RECTIFIER AND PHASE CONTROL TUBE Filed Sept. 23, 1955 INVENTOR fleweyfl Afflow/es.

wnwzssas;

ATTORNEY Patented Apr. 27, 1937 PATENT QEHQE CRYSTAL STARTER RECTIFIER AND PHASE CONTROL TUBE Dewey D. Knowles, Wilkinsburg, Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application September 23, 1933, Serial No. 690,701

9 Claims.

My invention relates to control apparatus and it has particular relation to apparatus for starting and controlling the operation of an electric discharge device of the type incorporating a starting electrode.

An electric discharge device of the type to which my invention is particularly applicable comprises an anode composed of carbon or other material, a cathode composed preferably of mercury, and a starting electrode preferably a crystal or other refractory material having a resistivity high compared to the resistivity of mercury immersed in the mercury. The electrodes are all disposed in a highly evacuated gas tight container in which, for certain purposes not involved in the present invention, a gas such as carbon monoxide for example may be present at a low pressure. When a potential of predetermined magnitude is impressed between the mercury electrode and the anode, and a current of predetermined magnitude is transmitted between the starting electrode and the mercury in a direction such that the starting electrode is electrically positive, a discharge is initiated between the mercury electrode and the cooperative anode. In the usual tube the starting current between the starting electrode and the mercury is of the order of from 5 to 50 amperes and consequently a dimcult problem is involved in providing the apparatus necessary for the transmission of the starting current. In accordance with the teachings of the prior art the potential supplied between the anode and the cathode (which shall hereinafter be designated as the principal potential) is of the alternating type. On the other hand, direct current is transmitted between the starting crystal and the mercury (which shall hereinafter be designated as the starting current). To provide the starting current, a rectifier is inserted between the source of principal potential and the starting elements. By reason of the fact that the starting current is comparatively high the practice has been, in the past, to provide a rectifier of the hot cathode gas-filled type of comparatively large current-carrying capacity. The energy consumed by this element in its operation renders the system rather expensive to the user.

Moreover, to prevent deterioration of the emissive surface, in a gas-filled hot-cathode electric discharge device, the cathode must be heated to a predetermined temperature before potential is supplied between the anode and the cathode. By reason of the magnitude of current involved, the cathode of the rectifier that is in accordance with the teachings of the prior art utilized in the starting circuit of the electric discharge device is of comparatively bulky structure. 'Such a cathode requires considerable time for heating to the proper emission temperature, and for this reason it has been the custom in apparatus constructed in accordance with the teachings of the prior art to provide a timing element to delay the application of potential to the rectifier for a certain interval of time after the current is applied to heat the cathode.

It is accordingly an object of my invention to provide a starting system for an electric discharge device of the type incorporating a starting electrode in which it shall be possible to utilize a rectifying element of comparatively small current-carrying capacity.

Another object of my invention is to provide a starting network for an electric discharge device, of the type incorporating a starting electrode through which a comparatively large starting current must be transmitted to initiate a discharge in which the necessary rectifying element shall be of small current-carrying capacity.

An incidental object of my invention is to provide a circuit for supplying starting current to an electric discharge device of the type incorporating a starting electrode, in which an element for timing the application of principal potential to the electrodes of the rectifying element in the starting circuit shall not be necessary.

More concisely stated, it is an object of my invention to provide for an electric discharge device of the type incorporating a starting electrode, a starting circuit of simple and inexpensive structure.

My invention arises from the application of the fact that the starting current need only be transmitted through the starting electrode and the cathode for a comparatively short interval of time to initiate the discharge in the electric discharge device. In accordance with my invention, I provide a starting network incorporating a rectifying element of small capacity which may be an electric discharge device either of the gas-filled or high-vacuum type or a voltaic element such as a copper copper-oxide Rectox unit. The rectifier is connected in series with a capacitor, and the network including the rectifier and the capacitor are connected to a power supply source. The capacitor, in turn, comprises one arm of a closed network, of which a spark discharge device, the starting electrode of the electric discharge device, and the cathode comprise the other arms. Under certain circumstances the discharge device in the network may be an open air gap.

I have found that the spark discharge tube may, with advantage, be an ordinary networkprotector tube such as the Westinghouse DKX- 640. This tube incorporates two cold electrodes immersed in a gaseous medium at a pressure of from 1 to 3 centimeters of mercury.

In defining such a tube as a spark discharge tube, I am following the accepted definition in the art as explained on page 49 of Fender: Handbook for Electrical Engineers, second edition (1922) John Wiley & Sons: A spark is also an incandescent, vapor bridge, but it differs from an arc, in not depending upon the electrodes for its material medium.

In operation, current is transmitted through the rectifier to charge the capacitor. When the potential impressed between the plates of the capacitor attains a high enough value, the spark discharge device becomes energized and current is transmitted between the starting electrode and the cathode to start the discharge in the electric V discharge device.

If it is desired to control the current output of the electric discharge device, the starting network may be energized from a phase shift circuit. By the operation of this circuit the instant at which the starting current is transmitted may be adjusted to any point in the half-cycles of principal potential applied to the principal electrodes of the electric discharge device.

The discharge initiated between the anode and the cathode of an electric discharge device of the type involved here persists only as long as the potential impressed between the anode and the cathode of the electric discharge device is of such magnitude and polarity as to maintain the discharge. When the principal potential becomes so low as not to support the discharge or becomes negative, the discharge is interrupted. It is apparent from the above consideration that the discharge in the electric discharge device must be initiated during every cycle of principal potential applied to. the electric discharge device if current is to be transmitted through the device during the positive half of each of the cycles.

The novel features that I consider characteristic of my invention are set forth with particularity in the appended claims. The invention, itself, however, both as to its organization and its methods of operation, together with additional objects and advantages thereof will best be understood from the following description of specific embodiments when read in connection with the accompanying drawing, in which:

Fig. 1 is a diagrammatic view showing an embodiment of my invention, and

Fig. 2 is a diagrammatic view showing a modification of my invention.

The apparatus shown in Fig. 1 comprisesan electric discharge device I incorporating an anode 3, preferably of carbon although other metals such as iron may be utilized, a cathode 5, preferably of mercury although other materials such as tin, zinc or lead might be utilized, and a starting electrode 1, preferably a crystal of carborundum or boron carbide or a suitably formed rod of these or similar materials ground and pressed together, although other materials such as globar rod material, Nernst filament material (rare earth compounds plus a binder) ferro-silicon, galena, zircomium resistor material, iron pyrites,- (iron sulfides) iron oxides, pencil lead (graphite plus edifying results in this capacity, a number of additional materials may, with advantage, also be utilized.

To return to the circuit the principal potential is supplied between the anode 3 and the cathode 5 of the electric discharge device 5 from a secondary section 9 of a suitable power supply transformer H. The principal electrodes 3 and 5 are connected to the terminals of the secondary section 9 through a load It of any desired character, and through a current limiting resistor IS. The starting system is composed of an open network I! comprising a rectifier l9 and a capacitor 2| connected in series and a closed network 23 of which the capacitor 2! is one arm, a gas-filled spark discharge device 25 is another arm, and the starting crystal 1 and its cooperative mercury electrode 5 comprises the remaining arm. The anode 2! of the rectifier I9 is connected directly to the anode 3 of the electric discharge device l and the capacitor 2| is connected directly to the anode I of the electric discharge device. a

When power is supplied to the system the capacitor 2| is charged through the rectifier H] from the secondary section 9 and when the potential difference between its plates attains a sufiicient value, the spark discharge device 25 becomes energized and starting current is transmitted through the starting electrode I. When current of proper magnitude is transmitted between the starting crystal 1 and its cooperative electrode 5 for only a short interval of time, a discharge is initiated between the principal electrodes 3 and 5 of the electric discharge device I and the load I3 is supplied with power. It is to be noted that since the capacitor 2! is in a 9 closed network 23 with the spark discharge device 25, the mercury electrode 5 and the starting crystal 1, the potential impressed between the plates of the capacitor 2| is substantially equivalent to the potential impressed between the electrodes of the spark discharge device 25.

While the rectifier l9 and the capacitor 2! may be comparatively small, their related magnitudes should depend onthe characteristic and the magnitude of the current to be transmitted through the load l3. If the current supplied to the load is is to be such that the discharge in the electric discharge device I must be initiated every cycle, the magnitude of the potential supplied, the current-carrying capacity of the rectifier l9 and the electrical capacity of the capacitor 2i should be of such magnitude with respect to the spark discharge device that the latter becomes energized every cycle. If the current necessary is such that it may be supplied at a periodicity smaller than the periodicity of the source, it is apparent that the capacitor 2! in the starting network 23 may be of such magnitucle as to be charged by impulses transmitted through the rectifier I9 during a series of half cycles during which the anode 21 of the rectifier is electrically positive. The charge thus supplied to the capacitor 2| is prevented from leak- 5 ing away by the rectifier [9 in series therewith until it attains such a value that the glow discharge device 25 becomes energized and the discharge in the electric discharge device I is initiated.

10 In the systems in which it is necessary that current be supplied to the load 13 during each positive half cycle of principal potential supplied to the electric discharge devicel, it may be desirable that the magnitude of the current be 15 controlled. In such a case a system of the type shown in Fig. 2 may be provided.

This system incorporates, in addition to the elements of the system shown in Fig. 1, a phase shift circuit 29 through which power is supplied to the starting system. The circuit 29 includes a secondary section 3! of the power supply transformer H between the terminals of which an open network including a resistor 33 and a variable capacitor in series with the resistor is connected. The phase shift circuit 29 is couplied to the starting system, through a starting transformer 31, the secondary 39 of which is connected across the series network I! including the rectifier l5 and the capacitor 2|, through a suitable current-limiting resistor 4|. As in the system shown in Fig. 1, the capacitor 21 is in the present case also connected in the closed network 23 incorporating the spark discharge device 25, the starting crystal '1 and the cathode 5 of the electric discharge device I.

The primary 43 of the starting transformer 31 is connected between the junction point 45 of the resistor 33 and the variable capacitor 35 of the phase shift circuit 29 and the intermediate tap 41 of the secondary section 3| of the power supply transformer II that is incorporated in the starting system.

The phase relationship between the potential supplied by the starting transformer 31 and the 45 principal potential may be adjusted by varying the capacitor 35 in the phase shift circuit 29. The point in the half cycle of positive principal potential at which the capacitor becomes sufficiently charged to energize the spark discharge device 25, may, therefore, be determined by adjusting the capacitor 35, and the current supplied to the load I3 may thus be determined.

In the embodiments described hereinabove, my invention has been shown as applied in particular to systems involving half-wave rectifiers. It is apparent that my invention may be applied equally as well to a full-wave rectifying system.

Moreover, in lieu of the asymmetric discharge device that is shown as utilized in the above described embodiments of my invention, symmetrically conducting units may be provided. A symmetrically conductive electric discharge device, in general, comprises a U-shaped tube in both arms of which a mercury electrode and a cooperating starting crystal are disposed. The potential impressed between the two mercury electrodes is alternately of one polarity and of opposite polarity, and consequently one or the other of the electrodes operates as an anode while the remaining electrode operates as a cathode. Such a device may be utilized in cases where the load is capable of taking alternating current and where it is desirable that the output of the electric discharge device be controlled. It is apparent that asymmetric electric discharge devices of the type described hereinabove will be, in practice, preferably utilized with a system of the type shown in Fig. 2.

Although I have shown and described certain specific embodiments of my invention, I am fully aware that many modifications thereof are possible. My invention, therefore, is not to be restricted except insofar as is necessitated by the prior art and by the spirit of the appended claims.

I claim as my invention:

1. In combination a set of electrodes between which a discharge is to be initiated, means for initiating the discharge including a plurality of electrodes disposed in contact with each other and network means, including a discharge device of the spark discharge type connected in series with said last-named set of electrodes, energy storing means connected in parallel with the network means including said spark discharge device and said last-named set of electrodes and means for supplying energy to said energy storing means, for controlling the transmission of a current between said last-named set of electrodes.

2. In combination, a set of electrodes between which a discharge is to be initiated, means for supplying an alternating potential between said set of electrodes, a network through which a current is to pass to initiate said discharge, said network including a plurality of electrodes in contact with each other, a spark discharge device and a capacitor all connected in series with each other, and means coupled to said network for charging said capacitor.

3. In combination, a set of electrodes between which a discharge is to be initiated, means for supplying an alternating potential between said set of electrodes a network through which a current is to pass to initiate said discharge, said network including a plurality of electrodes in contact with each other, a spark discharge device and a capacitor all connected in series with each other, and means including rectifying means coupled to said network and said potential-supply means for charging said capacitor.

4. A combination of electrodes between which a discharge is to be initiated, another combination of electrodes between which a current is to be transmitted to initiate said discharge, said last-named combination of electrodes being in contact with each other and one of said electrodes having a resistance high in comparison with the other, and means including a discharge device having cold electrodes for controlling the transmission of a current between said lastnamed combination of electrodes.

5. A combination of electrodes between which a discharge is to be initiated, another combination of electrodes between which a current is to be transmitted to initiate said discharge, said last-named combination of electrodes comprising a mercury electrode and an electrode having a resistance high in comparision with the resistance of mercury immersed in said mercury electrode, and means including a discharge device having cold electrodes for controlling the transmission of a current between said last-named set of electrodes.

6. A combination of electrodes between which a discharge is to be initiated, another combination of electrodes between which a current is to be transmitted to initiate said discharge, said last-named combination of electrodes comprising a mercury electrode and an electrode of a material that is not Wetted by mercury and has a resistance high compared to the resistance of the mercury immersed in said mercury electrode, and means including a discharge device having cold electrodes for controlling the transmission of a current between said last-named set of electrodes.

'7. A combination of electrodes between which a discharge is to be initiated, another combination of electrodes between which a current is to be transmitted to initiate said discharge, said last-named combination of electrodes comprising an-electrode of mercury and an electrode having a resistivity of at least .004 ohm per inch cube, and means including a discharge device having cold electrodes for controlling the transmission of a current between said last-named set of electrodes.

8. A combination of electrodes between which a discharge is to be initiated, another combination of electrodes between which a current is to be transmitted to initiate said discharge, said last-named combination of electrodes being in contact with each other and one of said electrodes having a resistance high in comparison with the other, and means including a discharge device having electrodes, immersed in a gaseous medium. at a pressure of from 1 to 3 centimeters of mercury, for controlling the transmission of a current between said last-named combination of electrodes.

9. In combination, a set of electrodes between which a discharge is to be initiated, means for initiating the discharge including an electrode disposed in contact with one of said first mentioned electrodes and network means, including a spark discharge device, connected in series with said contacting electrode, energy storing means connected in parallel with the network including said spark discharge device and said last-named set of electrodes and means for supplying energy to said energy storing means for controlling the transmission of a current between said electrodes in contact with each other.

DEWEY D. KNOWLES. 

